What is a Periprosthetic Knee Infection?
A very small percentage of patients (less than 1%) who undergo knee replacement may develop an infection around the knee joint. This infection is called a periprosthetic knee infection.
How does a Periprosthetic Knee Infection Occur?
Your immune system is usually able to protect the body from bacteria or other infectious organisms by attacking it through the lymph system or blood stream. However, your knee prosthesis, which is made of metal or plastic, does not have any blood vessels or lymphatic drainage, making it difficult for the immune system to gain access to and destroy these organisms. The bacteria can then multiply and cause the failure of the knee prosthesis.
Causes of Periprosthetic Knee Infections
A periprosthetic knee infection may occur immediately after the surgery or even many years later. The most common way bacteria or any other infectious organism reach the knee joint is through:
- Breaks in the skin
- Dental procedures such as tooth extraction
- Other surgeries
Risk factors for Periprosthetic Knee Infections
Factors that increase your risk of developing a periprosthetic knee infection are:
- Immunodeficiency disorders (e.g. HIV or lymphoma)
- Diabetes
- Peripheral vascular disease
- Obesity
- Immunosuppressive treatments
Symptoms of Periprosthetic Knee Infections
You may have developed a periprosthetic knee infection if you notice the following signs and symptoms around your knee joint:
- Pain and stiffness
- Redness and warmth
- Fever and chills
- Weakness
Diagnosis of a Periprosthetic Knee Infection
Your doctor will discuss your symptoms, ask about your medical history and perform a physical examination. Imagining studies such as X-rays and laboratory tests to identify the infection may also be ordered. Your doctor may also draw out fluid from your knee for a microscopic examination.
Treatment of Periprosthetic Knee Infections
The various treatment options for periprosthetic knee infections include:
Nonsurgical Treatment of Periprosthetic Knee Infection
If only the skin and the underlying soft tissue is infected, oral or intravenous antibiotics may be enough to treat the condition.
Surgical Treatment of Periprosthetic Knee Infection
If the infection has penetrated the deeper tissues around the knee joint, surgical treatment is necessary. The various surgical treatment options include:
- Debridement for Periprosthetic Knee Infection
- When the deep infection is diagnosed early, a surgical washout and debridement (removal of infected debris and dead tissue) may be all that is required to treat the condition. The knee implant is thoroughly cleaned during this procedure and any plastic liners or spacers may be replaced.
- Staged-Surgery for Periprosthetic Knee Infection
- If the periprosthetic infection is diagnosed at a later stage, a 2-staged surgery may be performed. The first stage involves removal of the knee implant, washout of the knee joint, placement of an antibiotic spacer, which maintains the integrity of the joint, and the administration of intravenous antibiotics. The second stage, which occurs a few weeks later, is the placement of the new knee prosthesis after the removal of the antibiotic spacer and a surgical washout of the knee.
Single-Stage Surgery for Periprosthetic Knee Infection
During this procedure, the infected knee implant is removed, the knee joint is washed out, and the new implant is placed within the knee. This relatively new method of treating a periprosthetic knee infection is slowly gaining popularity.
Prognosis Periprosthetic Knee Infection Treatment
The prognosis for treatment of a periprosthetic knee infection is good if the infection is identified early and treated promptly. In case the infection has been present for some time, revision surgery and replacement of the knee prosthesis is usually necessary.